The present invention relates to a method of and an apparatus for manufacturing a glass fiber mat, in which a uni-directional fiber layer and a non-oriented or random fiber layer, which are laminated one upon the other, are needled to manufacture the glass fiber mat.
A manufacturing line for a glass fiber mat is arranged as follows. That is, a uni-directional fiber layer and a non-oriented or random fiber layer are laminated one upon the other, the laminated element is needled by a needler, and the uni-directional fiber and the non-oriented fiber layer are intertwined with each other, to manufacture a united glass fiber mat.
The conventional apparatus for manufacturing a glass fiber mat is shown in FIG. 13 of the attached drawings. In this case, at an initial or start-up end section of a mat manufacturing line, bundles of uni-directional fibers 2 are first supplied onto a belt conveyor 3 from a warp beam 1 about which bundles of glass fibers such as cakes, rovings or yarns are wound, to form a uni-directional fiber layer. Bundles of continuous glass long-fibers 4 shake down in random onto the uni-directional fiber layer to laminate a non-oriented fiber layer 5 thereon. Subsequently, the laminated element consisting of the uni-directional fiber layer and the non-oriented fiber layer 5 is passed through a dryer 6 and is dried thereby. The laminated element is fed to a needler 7 by which the uni-directional fiber layer and the non-oriented fiber layer 5 are intertwined with each other by means of needling. By doing so, the uni-directional fiber layer and the non-oriented fiber layer 5 are united together to form a glass fiber mat.
The glass fiber mat is used to manufacture an FRTP stampable sheet or plate, for example. The stampable sheet is manufactured such that the glass fiber mat is impregnated with a molten resin, by the well-known method as disclosed in Japanese Patent Publication No. SHO 63-15135, Japanese Patent Provisional Publication No. SHO 61-112642, the periodical "Plastic Age", pp 194, issued on April 1989, or the like. Further, the stampable sheet is cut or severed into a plurality of sheet elements each having a predetermined dimension or size, The stampable sheet is stamping-molded to a molded article such as a bumper beam for a vehicle or the like, which has high strength and high elasticity in one direction.
The molded article that is a final product, for example, the bumper beam, must be stable in performance, for example, in flexural strength of rupture. To this end, it is necessary that the bundles of glass fibers of the uni-directional fiber layer are regularly or orderly oriented in a direction in which the strength of the molded article is required. This is similarly required in the stampable sheet that is the plate for the molded article, or in the glass fiber mat which is employed to manufacture the stampable sheet. In short, it is necessary that, when the uni-directional fiber layer and the non-directional fiber layer are intertwined with each other by needling to form the glass fiber mat, the glass fiber bundles forming the uni-directional fiber layer are oriented in parallel relation to each other and equidistantly spaced apart as far as possible, in other words, without skewing or meandering, in the widthwise direction of the mat. The performance of the molded article depends upon the uniformity in orientation.
For the conventional method, however, the following problems arise. That is, although the glass fiber bundles are uniformly oriented in the widthwise direction of the mat at an entrance for the conveyor, when the non-oriented fiber layer shakes down onto the uni-directional fiber layer, is superimposed thereupon and passes through the dryer, the orientation is disturbed under the influence of hot air. Further, as the non-oriented fiber layer and the uni-directional fiber layer travel together with the conveyor and come to a location short of the needler, the orientation is further disturbed by vibration of the needler. Since, in the glass fiber mat needled under this condition, the glass fiber bundles forming the uni-directional fiber layer are extremely irregular or non-uniform in orientation, it is impossible for the stampable sheet produced by the use of the mat, to produce a molded article having its stable performance.